Objective: Weight change may be considered an effect of depression. In turn, depression may follow weight change. Deteriorations in health may mediate these associations. The objective was to examine reciprocal associations between depressed mood and weight change, and the potentially mediating role of deteriorations in health (interim hospitalizations and incident mobility imitation) in these associations. Methods: Data were from 2406 black and white men and women, aged 70-79 from Pittsburgh, Pennsylvania and Memphis, Tennessee participating in the Health, Aging and Body composition (Health ABC) study. Depressed mood at baseline (T1) and 3-year follow-up (T4) was measured with the CES-D scale. Three weight change groups (T1-T4) were created: loss (≥5% loss), stable (within ±5% loss or gain), and weight gain (≥5% gain). Results: At T1 and T4, respectively 4.4% and 9.5% of the analysis sample had depressed mood. T1 depressed mood was associated with weight gain over the 3-year period (OR:1.91; 95%CI:1.13-3.22). Weight loss over the 3-year period was associated with T4 depressed mood (OR:1.51; 95%CI:1.05-2.16). Accounting for deteriorations in health in the reciprocal associations between weight change and depressed mood reduced effect sizes between 16-27%. Conclusions: In this study, depressed mood predicted weight gain over three years, while weight loss over three years predicted depressed mood. These associations were partly mediated through deteriorations in health. Implications for clinical practice and prevention include increased awareness that depressed mood can cause weight change, but can also be preceded by deteriorations in health and weight change. © 2010 American Association for Geriatric Psychiatry.